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A273208
Number of active (ON, black) cells in n-th stage of growth of two-dimensional cellular automaton defined by "Rule 609", based on the 5-celled von Neumann neighborhood.
4
1, 4, 21, 29, 72, 84, 141, 168, 248, 289, 340, 377, 477, 525, 597, 629, 808, 908, 1081, 1153, 1233, 1356, 1469, 1497, 1692, 1873, 2016, 2149, 2324, 2521, 2676, 2641, 2952, 3220, 3504, 3604, 3900, 4020, 4176, 4320, 4564, 4896, 5072, 5244, 5560, 5932, 6041
OFFSET
0,2
COMMENTS
Initialized with a single black (ON) cell at stage zero.
REFERENCES
S. Wolfram, A New Kind of Science, Wolfram Media, 2002; p. 170.
MATHEMATICA
CAStep[rule_, a_]:=Map[rule[[10-#]]&, ListConvolve[{{0, 2, 0}, {2, 1, 2}, {0, 2, 0}}, a, 2], {2}];
code=609; stages=128;
rule=IntegerDigits[code, 2, 10];
g=2*stages+1; (* Maximum size of grid *)
a=PadLeft[{{1}}, {g, g}, 0, Floor[{g, g}/2]]; (* Initial ON cell on grid *)
ca=a;
ca=Table[ca=CAStep[rule, ca], {n, 1, stages+1}];
PrependTo[ca, a];
(* Trim full grid to reflect growth by one cell at each stage *)
k=(Length[ca[[1]]]+1)/2;
ca=Table[Table[Part[ca[[n]][[j]], Range[k+1-n, k-1+n]], {j, k+1-n, k-1+n}], {n, 1, k}];
Map[Function[Apply[Plus, Flatten[#1]]], ca] (* Count ON cells at each stage *)
CROSSREFS
Sequence in context: A376222 A304770 A316513 * A273270 A273246 A273299
KEYWORD
nonn,easy
AUTHOR
Robert Price, May 17 2016
STATUS
approved